( 160 ) 



silver case U^, from which it is insulated by flannel t/g^. A float F^^ 

 indicates the level of the liquid air, of which the inflow is regulated 

 through the cock P^ with pivot P^ and packing P, identical with 

 the cock mentioned above, except that the glass tube with cock is 

 replaced by a new-silver one P^. 



The evaporated air is drawn off through a stout copper tube P, 

 (comp. § 4è). The 2 outlet tubes B,^ and P,,, of the spiral Pjj and P,,, 

 (each 23 windings, internal diameler of tube 3.6 m.m., external diameter 

 5,8 m.m., length of each 6 M.) are soldered in the bottom. The 

 two inflow tubes P^ and P,„ are soldered in the new-silver cover, 

 on which the glass tube F^ covering the index F^^ of the cork 

 float Pgi are fastened with sealing wax (comp. for nitrogen Comm. 

 N". 83 IV, March '03, PI. VII). 



d. The forecooling regenerator spiral Cj, C^, C^, and C^ is 

 wound in -4 windings like A, wrapped in flannel and enclosed in the 

 cylinder of the new-silver case U^. The four windings (internal diam. 

 of the tubing 2.4 m.m., external diam, 3.8 m.m., number of laj'ers 81, 

 length of each tube 20 M.) branch oif at the soldered piece C^ from 

 the tube C^^, soldered in the cover of U^. They unite to the two 

 tubes C^a and C^b through which the hydrogen is led to the refri- 

 gerator. The axis of this spiral is a thin-walled new-silver tube Cj 

 shut at the top. 



The hydrogen blown off is expelled through the tube U^. 



e. The liquid hydrogen is collected in a new-silver reservoir L^, 

 fitting the vacuum glass L^, which by means of a little wooden block 

 Fy rests on the wood-covered bottom of the insulated case F^, which 

 is coated internally with paper F^^ and capoc Fja- Thanks to L^ 

 the danger of bursting for the vacuum glass is less than when the 

 hydrogen should flow directly from Pj into the glass Po a- This beaker 

 moreover prevents rapid evaporation in case the glass should burst 

 (comp. § 1). 



The level of the liquid hydrogen is indicated by a float Pjoo) 

 which by means of a silk cord L^.^, slung over the pulleys P^, 

 and Pjj is balanced by an iron weight P^^, moving in a glass 

 tube Fji, which can also be pulled up and down with a magnet 

 from outside. The float is a box L^^ of very thin new-silver, the 

 hook Pjoj is a bent capillary tube open at both ends and soldered 

 in the cover. The glass V^^ fits by means of India rubber on the 

 cylinder Fj,, which is connected with the case by means of a thin- 

 walled new-silver tube Fj^. 



The hydrogen is drawn off through the new-silver siphon tube JVji, 

 which is continued as the double-walled tube N^^ ^boi» leading 



